# Coredns Module

This is a filebeat module for coredns. It supports both standalone coredns deployment and 
coredns deployment in Kubernetes.

## Caveats

* Module is to be considered _beta_.

## Download and install Filebeat

Grab the filebeat binary from elastic.co, and install it by following the instructions.

## Deployment Scenario #1: coredns native deployment

Make sure to update coredns configuration to enable log plugin. This module assumes that coredns log
entries will be written to /var/log/coredns.log. Should it be not the case, please point the module 
log path to the path of the log file. 

Update filebeat.yml to point to Elasticsearch and Kibana. 
Setup Filebeat.
```
./filebeat setup --modules coredns -e
```

Enable the Filebeat coredns module
```
./filebeat modules enable coredns
```

Start Filebeat
```
./filebeat -e
```

Now, the Coredns logs and dashboard should appear in Kibana.


## Deployment Scenario #2: coredns for kubernetes 

For Kubernetes deployment, the filebeat daemon-set yaml file needs to be deployed to the 
Kubernetes cluster. Sample configuration files is provided under the `beats/deploy/filebeat` 
directory, and can be deployed by doing the following:
```
kubectl apply -f filebeat
```

#### Note the following section in the ConfigMap, make changes to the yaml file if necessary
```
  filebeat.autodiscover:
    providers:
      - type: kubernetes
        hints.enabled: true
        hints.default_config.enabled: false

  processors:
    - add_kubernetes_metadata:
        in_cluster: true
```

This enables auto-discovery and hints for filebeat. When default.disable is set to true (default value is false), it will disable log harvesting for the pod/container, unless it has specific annotations enabled. This gives users more granular control on kubernetes log ingestion. The `add_kubernetes_metadata` processor will add enrichment data for Kubernetes to the ingest logs.

#### Note the following section in the DaemonSet, make changes to the yaml file if necessary
```
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: filebeat
  namespace: kube-system
  labels:
    k8s-app: filebeat
spec:
  template:
    metadata:
      labels:
        k8s-app: filebeat
    spec:
      serviceAccountName: filebeat
      terminationGracePeriodSeconds: 30
      containers:
      - name: filebeat
        image: docker.elastic.co/beats/filebeat:%VERSION%
        args: [
          "sh", "-c", "filebeat setup -e --modules coredns -c /etc/filebeat.yml && filebeat -e -c /etc/filebeat.yml"
        ]
        env:
        # Edit the following values to reflect your setup accordingly
        - name: ELASTICSEARCH_HOST
          value: 192.168.99.1
        - name: ELASTICSEARCH_USERNAME
          value: elastic
        - name: ELASTICSEARCH_PASSWORD
          value: changeme
        - name: KIBANA_HOST
          value: 192.168.99.1
```

The module setup step can also be done separately without Kubernetes if applicable, and in that case, the args can be simplified to:
```
        args: [
          "sh", "-c", "filebeat -e -c /etc/filebeat.yml"
        ]
```

### Note that you probably need to update the coredns configmap to enable logging, and coredns deployment to add proper annotations. 

##### Sample ConfigMap for coredns:

```
apiVersion: v1
data:
  Corefile: |
    .:53 {
        log
        errors
        health
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods verified
           endpoint_pod_names
           upstream
           fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        proxy . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
kind: ConfigMap
metadata:
  creationTimestamp: "2019-01-31T21:02:57Z"
  name: coredns
  namespace: kube-system
  resourceVersion: "185717"
  selfLink: /api/v1/namespaces/kube-system/configmaps/coredns
  uid: 95a5d5cb-259b-11e9-8e5d-080027971f3c
```

#### Sample Deployment for coredns. Note the annotations.

```
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: coredns
spec:
  replicas: 2
  template:
    metadata:
      annotations:
        "co.elastic.logs/module": "coredns"
        "co.elastic.logs/fileset": "log"
        "co.elastic.logs/disable": "false"
      labels:
        k8s-app: coredns
    spec:
      <snipped>
```

